1. Field of the Invention
The present invention relates to a method, system, and program for copying file sets and related metadata to storage.
2. Description of the Related Art
In a distributed file system, clients share a global namespace addressing storage locations on distributed storage devices. A central server manages the distributed file namespace for the clients. For instance, a metadata server cluster comprised of multiple server devices may maintain the global namespace of a distributed file system stored in different storage pools for the clients. The global namespace is organized into filesets, which comprise file system directories and folders accessible to the clients for file operations. On the clients, the global namespace appears as a hierarchical file directory provided by the operating system running on the client. The clients would access the file metadata maintained by the metadata server when accessing the user data. Further details of a distributed file system using metadata servers is described in the International Business Machines Corporation (“IBM”) publication “IBM Total Storage: Introducing the SAN File System”, document no. SG24-7057-02 (December 2004).
To backup and copy data in a storage system, the storage locations including the file sets of the user data to copy and the metadata for the file sets, may be copied by first halting all operations to the data to copy to ensure that the data is consistent as of a point-in-time, copying all the data to a backup location and then resume processing to the data to which operations were halted after completing the copying of all the data. File sets may be copied as part of a volume level copy or a file level point-in-time copy, such that only specified files or data blocks are subject to the point-in-time copy operation.
The drawback of this technique is that the data subject to the copying is unavailable during the copy operation, which can take a relatively long time to complete, especially for enterprise systems which require continuous availability of user data.
Another copy option for copying user data is to perform a FlashCopy® operation. FlashCopy® is a registered trademark of IBM. A FlashCopy operation involves creating a data structure indicating a relationship between the source and target data to copy, and then after the relationship is established by creating the data structure, allowing access to the underlying data before the data is actually copied. The FlashCopy operation may specify that the point-in-time copy operation is performed with respect to a volume.